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colmmacc's profile
Colm MacCárthaigh
Colm MacCárthaigh
Colm MacCárthaigh
@colmmacc

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Colm MacCárthaigh

@colmmacc

AWS, Apache, Crypto, Irish Music, Haiku, Photography

Seattle
notesfromthesound.com
Joined April 2008

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    1. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Every big program I've designed has been heavily informed by these concepts. The core memory management of I/O of s2n uses all of these ideas .. even though it's written in C. https://github.com/awslabs/s2n/blob/master/docs/DEVELOPMENT-GUIDE.md#a-tour-of-s2n-memory-handling-blobs-and-stuffers …

      1 reply 0 retweets 15 likes
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    2. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Read SICP, learn about Erlang, look at FP features in Javascript and Rust. All super super worth it.

      1 reply 4 retweets 27 likes
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    3. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      O.k. item FOUR ... check everything and bail on bad. What do I mean by this? I mean every time you call a function, a library routine, or whatever ... check for errors! don't mask exceptions. Anticipate "that shouldn't happen" errors.

      1 reply 2 retweets 16 likes
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    4. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      If there are invariants that should hold in your program, check those too! You can pretty much never check things too much. And if things don't add up .... bail! Be very very defensive in your programming.

      1 reply 1 retweet 8 likes
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    5. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      This also relates to a simple programming tip. It can be easy to fall into a pattern of ... if (condition1 == good) { ... if (condition2 == good) { ... if (condition3 == good) { do_something(); but this is bad and becomes dangerous.

      1 reply 2 retweets 10 likes
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    6. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Instead do: if (condition1 != good) { bail(); } ... if (condition2 != good) { bail(); } if (condition3 != good) { bail(); } usually makes context much clearer, avoids nesting confusion, and builds in that pattern of bailing!

      1 reply 1 retweet 48 likes
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    7. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      o.k. last piece of advice and it is ... don't write "what" comments, write "why" comments. If you have to comment on what your program is doing, then the code itself was not readable! Instead use comments to provide context.

      1 reply 2 retweets 29 likes
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    8. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Use readable variable names that are nouns and meaningful function names that are verbs. The code doesn't have to be poetry, but it can absolutely be easy to follow. Give your future self an easier time. Code is written to be read.

      1 reply 3 retweets 18 likes
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    9. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Very very rarely there is code that can't be easily read; if you're using bitwise operators as part of cryptography or compression or something, for example. Comment those with a "WTF is this doing" ... be very very verbose. But that's the only exception I've found!

      1 reply 2 retweets 9 likes
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    10. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      Which brings me to the $1000 programming contest! 3 prizes: $500, $300, $200 for the most readable, easy to follow, tested, Apache Software License 2.0'd, implementation of @lemire's nearly division-less RNG.https://lemire.me/blog/2019/06/06/nearly-divisionless-random-integer-generation-on-various-systems/ …

      4 replies 35 retweets 71 likes
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      Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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      I hope he doesn't mind because I didn't ask! I've chosen @lemire's algorithm because it is awesome and ground breaking, very short, and intrinsically hard to follow if you're not into the math.

      11:03 AM - 23 Jul 2019
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        2. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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          His blog post contains a 14 line implementation in C, and there's also a paper getting into it: https://arxiv.org/abs/1805.10941 , so there's great material to start from. But how can we make it more readable and easy to follow for a beginner or non-math-expert? how can we test it?

          1 reply 1 retweet 20 likes
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        3. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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          Have at it and give it a go! Any programming language you like. Apache Software License so that it can be included in other things. Closing date: September 1st 2019.

          2 replies 1 retweet 5 likes
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        4. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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          Message me a gist, or a link, or send me an e-mail, whatever works ... and we can talk readability and testing about it too!

          1 reply 1 retweet 5 likes
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        5. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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          For further reference: here's my rejection sampling RNG implementation with more comments than code. https://github.com/awslabs/s2n/blob/master/utils/s2n_random.c#L182 … End of thread!

          5 replies 1 retweet 14 likes
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        6. End of conversation
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        2. Daniel Lemire‏ @lemire 23 Jul 2019
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          Replying to @colmmacc

          This sounds like fun. Can I blog about your contest?

          1 reply 0 retweets 1 like
        3. Colm MacCárthaigh‏ @colmmacc 23 Jul 2019
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          Replying to @lemire

          Absolutely! ❤️ your algorithm and this is my way of getting more people to see and appreciate it, and despite being so small and simple, it's in the space of "intrinsically challenging to make understandable".

          0 replies 0 retweets 0 likes
        4. End of conversation
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        2. sunnygleason‏ @sunnygleason 24 Jul 2019
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          Replying to @colmmacc @lemire

          As I look at the algorithm I wonder: have you thought about a special case for “power-of-2” (which presumably could just use right shift)? If same range is frequently re-used, the shift distance could be memoized...

          2 replies 0 retweets 0 likes
        3. Colm MacCárthaigh‏ @colmmacc 24 Jul 2019
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          Replying to @sunnygleason @lemire

          It's a fairly standard optimization and @lemire mentions it in the paper. In practice though it doesn't work out, it only optimizes 63 values out of 2^64, which is minuscule; the cost of the branch more than undoes that on average.pic.twitter.com/Wg0fQSI79l

          1 reply 0 retweets 2 likes
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        1. Daniel Lemire‏ @lemire 23 Jul 2019
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          Replying to @colmmacc

          :-)

          0 replies 0 retweets 1 like
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